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When a perfect voltmeter is connected in series, what effect does it have?

  1. Reduces voltage

  2. Increases current flow

  3. Prevents the flow of current

  4. Measures voltage across a load

The correct answer is: Prevents the flow of current

A perfect voltmeter is designed to have infinite resistance, which means it draws no current when connected to a circuit. When a voltmeter is connected in series, its high resistance prevents any current from flowing through the circuit. This results in the voltmeter not affecting the circuit’s behavior, but it also means that the circuit is open, effectively stopping current flow. This characteristic allows it to measure voltage without altering the original circuit parameters. Understanding this principle highlights why a perfect voltmeter, by design, leads to the prevention of current flow when connected in this manner.